Imaging device, focusing control method, and focusing control program

ABSTRACT

An imaging device includes: a lens including a focus lens capable of moving in an optical axis direction; an imaging element imaging a subject through the focus lens; and a processor controlling the focus lens and the imaging element and selectively performing one of acceleration and deceleration control such that a movement speed of the focus lens is decelerated after the movement speed is accelerated and constant speed control such that the movement speed of the focus lens is constant by controlling the movement speed based on evaluation values, lens performance information, and first imaging performance information so as to move the target lens to a target position.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of and claims the priority benefit ofU.S. patent application Ser. No. 16/011,647, filed on Jun. 19, 2018, nowallowable, which is a continuation of International Application No.PCT/JP2016/082696 filed on Nov. 2, 2016, and claims priority fromJapanese Patent Application No. 2015-249618 filed on Dec. 22, 2015. Theentire disclosures of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to an imaging device, a focusing controlmethod, and a computer readable medium storing a focusing controlprogram.

2. Description of the Related Art

In recent years, with an increase in resolution of imaging elements,such as a charge coupled device (CCD) image sensor and a complementarymetal oxide semiconductor (CMOS) image sensor, there has been a rapidincrease in demand for information devices having an imaging function,such as a digital still camera, a digital video camera, and asmartphone. The information devices having an imaging function describedabove are referred to as imaging devices.

In these imaging devices, as a focusing control method which focuses ona main subject, a contrast auto focus (AF) method or a phase differenceAF method is employed.

The contrast AF method is a method which calculates evaluation values ofsharpness from captured image signals acquired in movement positions ofa focus lens while moving the focus lens in an optical axis directionand determines a lens position having a highest evaluation value as atarget position of the focus lens.

JP1995-7650A (JP-H7-7650A) describes an imaging device that performsfocusing control through the contrast AF method.

In a case where the focus lens is moved in order to acquire theevaluation values, the imaging device performs acceleration anddeceleration control such that the focus lens is moved at a high speedfor a period during which a change in evaluation value is small and thefocus lens is moved at a low speed for a period during which a change infocusing evaluation value is large. According to the acceleration anddeceleration control, it is possible to increase the speed of thefocusing control while securing focusing accuracy.

JP1989-239514A (JP-H1-239514A) describes a system that controls amovement speed of a focus lens in a case where the focus lens is movedin order to search for a target position based on information stored inan imaging device and information stored in a lens device attached tothe imaging device.

JP2007-299997A describes an imaging device that controls a movementrange of a focus lens in a case where the focus lens is moved in orderto search for a target position.

SUMMARY OF THE INVENTION

In order to perform the focusing control at a high speed through thecontrast AF method, the movement speed of the focus lens at the time ofa search operation when the focus lens is moved from a nearest end to aninfinity end in order to acquire the evaluation values may be increased.

However, even though only the movement speed of the focus lens is simplyincreased, in a case where an interval at which the captured imagesignals are sampled by the imaging element is long, the number ofevaluation values capable of being calculated is reduced. Thus,determination accuracy of the target position is not able to beimproved.

The increasing of the movement speed of the focus lens at the time ofthe search operation and the reducing of the sampling interval of thecaptured image signals during the movement of the focus lens (theincreasing of the frame rate) are effective. However, in a case wherethe frame rate is increased, it is necessary to increase the movementspeed of the focus lens with the increase in the frame rate.

As stated above, in a case where the movement speed becomes high, ittakes a time to decelerate the movement speed after the movement speedis accelerated. Thus, as described in JP1995-7650A (JP-H7-7650A), in acase where the acceleration and deceleration control is performed, themovement speed of the focus lens may not be sufficiently decreased whilethe focus lens passes through a lens position in which the evaluationvalue is near the peak.

As a result, the number of evaluation values to be sampled is not ableto be sufficiently secured near the lens position in which theevaluation value becomes the peak, and thus, the determination accuracyof the target position is deteriorated.

In order to improve the determination accuracy of the target position,after the focus lens is moved from the nearest end to the infinity end,it is necessary to increase the number of evaluation values to besampled by performing control such that the focus lens is returned fromthe infinity end to the nearest end in a state in which a desired value(a value at which a sufficient number of evaluation values is acquired)is set as the movement speed of the focus lens. However, in a case wherethis control is performed, a time taken to complete the focusing controlis prolonged.

Accordingly, in a case where the acceleration and deceleration controlis performed, the combination of the movement speed of the focus lensduring the search operation with the frame rate is optimized, and thus,it is important to set a balance between the focusing accuracy and thefocusing speed to be in a best state.

However, in the imaging device to which the lens device is detachablyattached, driving performance of the focus lens varies depending on thelens device, and a frame rate capable of being set varies depending onthe imaging device.

Thus, the acceleration and deceleration control is performed in somecombinations of the lens device with the imaging device, and thus, thereare some cases where it is difficult to achieve both the high focusingaccuracy and the increase in focusing speed.

JP1995-7650A (JP-H7-7650A) does not take account of the relationshipbetween the frame rate and the movement speed of the focus lens or acase where the lens device is detachably attached.

The imaging device described in JP1989-239514A (JP-H1-239514A) does notchange the movement speed of the focus lens at the time of the searchoperation.

The imaging device described in JP2007-299997A does not change themovement speed of the focus lens at the time of the search operation.This imaging device does not take account of the case where the lensdevice is detachably attached.

The present invention has been made in view of such circumstances, andan object of the present invention is to provide an imaging device, afocusing control method, and a focusing control program which arecapable of constantly realizing focusing control at a high speed withhigh accuracy irrespective of being combined with a lens device.

An imaging device according to the present invention is an imagingdevice having a lens, an imaging element, and a processor. The lensincludes a focus capable of moving in an optical axis direction. Theimaging element that images a subject through the focus lens. Theprocessor is configured to control the focus lens and the imagingelement to acquire captured image signals by causing the imaging elementto image the subject for each position of the focus lens while movingthe focus lens, calculate evaluation values for determining a targetposition of the focus lens based on the captured image signals,determine the target position of the focus lens based on the evaluationvalues, acquire lens performance information indicating focusingperformance of the focus lens from the lens, where one of accelerationand deceleration control are selectively performed such that a movementspeed of the focus lens is decelerated after the movement speed isaccelerated and constant speed control such that the movement speed ofthe focus lens is constant by controlling the movement speed based onthe evaluation values, the lens performance information, and imagingperformance information indicating number of captured image signals readout per unit time in a case where the captured image signals arecontinuously read out from the imaging element or a reading interval ofthe captured image signals so as to move the focus lens to the targetposition.

A focusing control method according to the present invention is afocusing control method using an imaging device having a lens includinga focus lens capable of moving in an optical axis direction and havingan imaging element which images a subject through the focus lens. Themethod includes a search control step of controlling the focus lens andthe imaging element to acquire captured image signals by causing theimaging element to image the subject for each position of the focus lenswhile moving the focus lens, an evaluation value calculation step ofcalculating evaluation values for determining a target position of thefocus lens based on the captured image signals, a target positiondetermination step of determining the target position of the focus lensbased on the evaluation values, and a lens information acquisition stepof acquiring lens performance information indicating focusingperformance of the focus lens from the lens. In the search control step,any one of acceleration and deceleration control such that a movementspeed of the focus lens is decelerated after the movement speed isaccelerated and constant speed control such that the movement speed ofthe focus lens is constant is selectively performed by controlling themovement speed based on the evaluation values, the lens performanceinformation, and imaging performance information indicating the numberof captured image signals read out per unit time in a case where thecaptured image signals are continuously read out from the imagingelement or a reading interval of the captured image signals so as tomove the focus lens to the target position.

A focusing control program according to the present invention is aprogram causing a computer included in an imaging device having a lensincluding a focus lens capable of moving in an optical axis directionand having an imaging element which images a subject through the focuslens to control the focus lens and the imaging element to acquirecaptured image signals by causing the imaging element to image thesubject for each position of the focus lens while moving the focus lens,calculate evaluation values for determining a target position of thefocus lens based on the captured image signals, determine the targetposition of the focus lens based on the evaluation values, acquire lensperformance information indicating focusing performance of the focuslens from the lens, where one of acceleration and deceleration controlare selectively performed such that a movement speed of the focus lensis decelerated after the movement speed is accelerated and constantspeed control such that the movement speed of the focus lens is constantby controlling the movement speed based on the evaluation values, thelens performance information, and imaging performance informationindicating number of captured image signals read out per unit time in acase where the captured image signals are continuously read out from theimaging element or a reading interval of the captured image signals soas to move the focus lens to the target position.

According to the present invention, it is possible to provide an imagingdevice, a focusing control method, and a focusing control program whichare capable of constantly realizing focusing control at a high speedwith high accuracy irrespective of being combined with a lens device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing the schematic configuration of a digitalcamera as an example of an imaging device for describing an embodimentof the invention.

FIG. 2 is a functional block diagram of a system control unit 11 of thedigital camera shown in FIG. 1.

FIG. 3 is a graph showing an example of a change in movement speed of afocus lens at the time of acceleration and deceleration control.

FIG. 4 is a flowchart for describing an operation of the system controlunit 11 of the digital camera shown in FIG. 1.

FIG. 5 is a diagram showing a modification example of a function blockof a system control unit 11 shown in FIG. 2.

FIG. 6 is a flowchart for describing an operation of a system controlunit 11 of a digital camera according to a first modification example.

FIG. 7 is a flowchart for describing an operation of a system controlunit 11 of a digital camera according to a second modification example.

FIG. 8 is a flowchart for describing an operation of a system controlunit 11 of a digital camera according to a third modification example.

FIG. 9 shows the appearance of a smartphone which is an embodiment of animaging device of the invention.

FIG. 10 is an internal block diagram of the smartphone of FIG. 9.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, an embodiment of the invention will be described byreferring to the drawings.

FIG. 1 is a diagram showing the schematic configuration of a digitalcamera as an example of an imaging device for describing an embodimentof the invention.

The digital camera shown in FIG. 1 is an imaging device capable ofdetachably attaching a lens device 40 that has an imaging lens 1including a focus lens for focus adjustment, a stop 2, a lensinformation storage unit 3, a lens control unit 4, a lens drive unit 8,and a stop drive unit 9.

The imaging lens 1 and the stop 2 of the lens device 40 constitute animaging optical system. The imaging lens 1 includes at least the focuslens.

The focus lens is a lens that adjusts a focus position of the imagingoptical system by moving in an optical axis direction. In a case wherethe imaging lens consisting of a plurality of lenses are all-groupmoving type lens, and all the groups are focus lenses.

The lens control unit 4 of the lens device 40 is able to communicatewith a system control unit 11 of the digital camera in a wired orwireless manner.

The lens control unit 4 drives the focus lens included in the imaginglens 1 through the lens drive unit 8 or drives the stop 2 through thestop drive unit 9 according to a command from the system control unit11.

Lens performance information indicating focusing performance of the lensdevice 40 is stored in the lens information storage unit 3 of the lensdevice 40. The lens performance information will be described.

The digital camera includes an imaging element 5 which images a subjectthrough the imaging optical system of the lens device 40, such as a CCDtype or CMOS type, an analog signal processing unit 6 which is connectedto an output of the imaging element 5 and performs analog signalprocessing such as correlative double sampling processing, ananalog-to-digital conversion circuit 7 which converts the analog signaloutput from the analog signal processing unit 6 into a digital signal, astorage unit 12, an imaging element drive unit 10, the system controlunit 11, and an operating unit 14. The analog signal processing unit 6and the analog-to-digital conversion circuit 7 are controlled by thesystem control unit 11.

The system control unit 11 that generally controls the entire electriccontrol system of the digital camera drives the imaging element 5through the imaging element drive unit 10, and outputs a subject imagecaptured through the lens device 40, as captured image signals. Acommand signal from a user is input to the system control unit 11through the operating unit 14.

The system control unit 11 moves the focus lens included in the imaginglens 1 through the lens control unit 4 and the lens drive unit 8. Thesystem control unit 11 adjusts the amount of exposure by controlling theamount of aperture of the stop 2 through the lens control unit 4 and thestop drive unit 9.

A frame rate f_(body) which is the number of captured image signals tobe read out per unit time (for example, one second) in a case where amotion picture imaging is performed by the imaging element 5 and thecaptured image signals are continuously read out from the imagingelement 5 is stored in the storage unit 12. The frame rate f_(body)constitutes first imaging performance information.

The electric control system of the digital camera further includes amain memory 16 which includes a flash memory and a random access memory(RAM), a memory control unit 15 which is connected to the main memory16, a digital signal processing unit 17 which generates captured imagedata by performing interpolation calculation, gamma correctioncalculation, and the like on the captured image signals output from theanalog-to-digital conversion circuit 7, a compression/expansionprocessing unit 18 which compresses the captured image data generated bythe digital signal processing unit 17 in a Joint Photographic ExpertsGroup (JPEG) format or expands the compressed image data, an externalmemory control unit 20 to which a detachable recording medium 21 isconnected, and a display control unit 22 to which a display unit 23mounted on a camera rear surface or the like is connected.

The memory control unit 15, the digital signal processing unit 17, thecompression/expansion processing unit 18, the external memory controlunit 20, and the display control unit 22 are connected to one another bya control bus 24 and a data bus 25, and are controlled according tocommands from the system control unit 11.

FIG. 2 is a functional block diagram of the system control unit 11 inthe digital camera shown in FIG. 1.

The system control unit 11 includes a search control unit 110, anevaluation value calculation unit 111, a target position determinationunit 112, a focusing control unit 113, and a lens informationacquisition unit 114.

These functional blocks are formed by a focusing control program beingexecuted by a processor (computer) included in the system control unit11. The system control unit 11 constitutes a focusing control device.

The search control unit 110 causes the imaging element 5 to image thesubject for the positions of the focus lens while moving the focus lensby controlling the lens control unit 4, and acquires the captured imagesignals for the positions of the focus lens.

The evaluation value calculation unit 111 performs a filtering processon the captured image signals for the positions of the focus lensacquired by the search control unit 110, and calculates evaluationvalues for determining a target position of the focus lens based on thesignals on which the filtering process has been performed. For example,the evaluation values are acquired by calculating contrast values of thecaptured image signals acquired by performing the filtering process.

The target position determination unit 112 determines the targetposition of the focus lens based on the evaluation values calculated forthe positions of the focus lens by the evaluation value calculation unit111.

For example, the target position determination unit 112 acquires anevaluation value curve indicating the relationship between the positionsof the focus lens and the evaluation values for the subject to beingcaptured from the plurality of evaluation values calculated by theevaluation value calculation unit 111, and determines the position ofthe focus lens corresponding to a maximum point of the evaluation valuecurve, as the target position.

Alternatively, the target position determination unit 112 determines theposition of the focus lens at which a maximum evaluation value of theplurality of evaluation values is acquired, as the target position.

The focusing control unit 113 performs focusing control for moving thefocus lens to the target position determined by the target positiondetermination unit 112 by controlling the lens control unit 4.

The lens information acquisition unit 114 requests that the lens controlunit 4 is to transmit the lens performance information stored in thelens information storage unit 3, and acquires the lens performanceinformation transmitted from the lens control unit 4 according to thetransmission request.

The search control unit 110 selectively performs any one of accelerationand deceleration control such that a movement speed of the focus lens isdecelerated after the movement speed is accelerated and constant speedcontrol such that the movement speed of the focus lens is constant, asdriving control of the focus lens in a case where the focus lens ismoved in order to calculate the evaluation value.

The search control unit 110 determines whether to perform theacceleration and deceleration control or the constant speed controlbased on the lens performance information acquired by the lensinformation acquisition unit 114 and the frame rate f_(body) stored inthe storage unit 12.

FIG. 3 is a graph showing an example of a change in movement speed ofthe focus lens at the time of the acceleration and deceleration control.

In FIG. 3, a horizontal axis represents the position of the focus lens.A vertical axis on the left side in FIG. 3 represents the evaluationvalue calculated by the evaluation value calculation unit 111. Avertical axis on the right side in FIG. 3 represents the movement speedof the focus lens.

A reference A1 in FIG. 3 is a graph showing the relationship between themovement speed of the focus lens and the position of the focus lens. Areference A2 in FIG. 3 is a graph showing the relationship between theevaluation value and the position of the focus lens.

The search control unit 110 starts the movement of the focus lens fromthe reference position after moving the focus lens to a referenceposition (for example, a nearest end or an infinity end), andaccelerates the movement speed of the focus lens up to a first movementspeed V1.

In a case where the movement of the focus lens is started, the searchcontrol unit 110 monitors the evaluation value calculated by theevaluation value calculation unit 111, and determines whether or not achange in evaluation value is equal to or greater than a thresholdvalue.

For example, in a case where a difference between an evaluation valuecalculated in a current position of the focus lens and an evaluationvalue calculated in a previous position of the current position of thefocus lens is equal to or greater than a predetermined value, the searchcontrol unit 110 determines that the change in evaluation value is equalto or greater than the threshold value.

In the example of FIG. 3, the search control unit determines that thechange in evaluation value is equal to or greater than the thresholdvalue in a state in which the focus lens is present in a position X1.

In a case where it is determined that the change in evaluation value isequal to or greater than the threshold value, the search control unit110 decelerates the movement speed of the focus lens up to a secondmovement speed V2. In a case where it is determined that the change inevaluation value is not equal to or greater than the threshold value,the search control unit 110 does not decelerate the movement speed ofthe focus lens.

As stated above, the search control unit 110 performs the accelerationand deceleration control by controlling the movement speed of the focuslens based on the evaluation value calculated by the evaluation valuecalculation unit 111.

The first movement speed V1 and the second movement speed V2 shown inFIG. 3 and a deceleration a_(dec) (a value indicating the extent thatthe movement speed thereof decelerates per unit time) in a case wherethe movement speed of the focus lens decelerates are stored in the lensinformation storage unit 3, as the lens performance information.

As the second movement speed V2, a predetermined value is set within arange in which the number of evaluation values calculated by theevaluation value calculation unit 111 is able to secure focusingaccuracy.

As the first movement speed V1, a predetermined value which is greaterthan the second movement speed and is smaller than a driving limit ofthe focus lens is set.

As the deceleration a_(dec), a predetermined value is set such that themovement speed decelerates up to the second movement speed V2 from thefirst movement speed V1 before the evaluation value reaches a peak afterthe change in evaluation value which is equal to or greater than thethreshold value is started.

A maximum frame rate f_(acc) capable of being combined with theacceleration and deceleration control performed based on the firstmovement speed V1, the second movement speed V2, and the decelerationa_(dec) is included in the lens performance information. The frame rateface constitutes second imaging performance information.

In the lens device 40, the acceleration and deceleration control isperformed based on the first movement speed V1, the second movementspeed V2, and the deceleration a_(dec). Further, the evaluation valuesare calculated by reading out the captured image signals from theimaging element 5 according to the frame rate face, and the targetposition is determined. Thus, a balance between a focusing speed andfocusing accuracy can be in a best state.

Priority specification information Pmode indicating whether thecombination of the frame rate fact with the acceleration anddeceleration control or the combination of the frame rate which isgreater than the frame rate fact with the constant speed control ispreferentially performed is included in the lens performanceinformation.

A movable range of the focus lens is not the same for any device type oflens device 40. Thus, in some lens devices, the balance between thefocusing speed and the focusing performance may become better byperforming the constant speed control at a frame rate greater than theframe rate f_(acc), or the balance between the focusing speed and thefocusing performance may become better by performing the accelerationand deceleration control.

For example, in a lens device having a narrow movable range of the focuslens, it does not take time to move the focus lens from the nearest endto the infinity end even though the movement speed of the focus lens isconstant. Thus, in a case where the frame rate is high, the balancebetween the focusing speed and the focusing accuracy can be favorableeven though the acceleration and deceleration control is not performed.

In a lens device having a wide movable range of the focus lens, it takestime to move the focus lens from the nearest end to the infinity end ina case where the constant speed control is performed. Thus, the balancebetween the focusing speed and the focusing accuracy can be favorable byperforming the acceleration and deceleration control.

For this reason, the priority specification information Pmode dependingon characteristics of the lens device is included in the lensperformance information.

FIG. 4 is a flowchart for describing an operation of the system controlunit 11 of the digital camera shown in FIG. 1.

In a case where the lens device 40 is attached to the digital camera,the system control unit 11 acquires the maximum frame rate f_(body)capable of being set in the digital camera from the storage unit 12(step S1).

Subsequently, the lens information acquisition unit 114 of the systemcontrol unit 11 acquires the lens performance information including theframe rate f_(acc) and the priority specification information Pmode fromthe lens device 40 (step S2).

Subsequently, the search control unit 110 determines whether or not theframe rate f_(body) acquired in step S1 is greater than the frame ratef_(acc) acquired in step S2 (step S3).

In a case where the frame rate f_(body) is equal to less than the framerate f step S3: NO), face (the search control unit 110 sets the framerate f_(body) as the frame rate, and sets the acceleration anddeceleration control as the driving control (step S4).

In a case where the frame rate f_(body) is greater than the frame rate f(step S3: YES), the face search control unit 110 determines whether ornot the acceleration and deceleration control is preferentiallyperformed while referring to the priority specification informationPmode acquired by the lens information acquisition unit 114 (step S5).

In a case where the priority specification information Pmode isinformation for specifying that the constant speed control ispreferentially performed (step S5: NO), the search control unit 110 setsthe frame rate f_(body) as the frame rate, and sets the constant speedcontrol as the driving control (step S6).

As the movement speed of the focus lens at the time of the constantspeed control, the movement speed which is associated with the framerate f_(body) and is stored in the storage unit 12 in advance is used.

In a case where the priority specification information Pmode isinformation for specifying that the acceleration and decelerationcontrol is preferentially performed (step S5: YES), the search controlunit 110 sets the frame rate f_(acc) as the frame rate, and sets theacceleration and deceleration control as the driving control (step S7).

After step S4, step S6, and step S7, in a case where an instruction toperform AF is received, the search control unit 110 moves the focus lensand causes the imaging element 5 to perform the motion picture imagingaccording to the frame rates and the driving control set in step S4,step S6, and step S7.

The evaluation values are calculated based on the captured image signalsacquired during the motion picture imaging, and the target position ofthe focus lens is determined based on the evaluation value. The focusingcontrol unit 113 moves the focus lens to the determined target position,and thus, the AF according to the instruction is ended.

As stated above, according to the digital camera of FIG. 1, it ispossible to determine whether to perform the constant speed control orthe acceleration and deceleration control and how to set the frame ratebased on the lens performance information acquired from the lens device40 and the frame rate f_(body) stored in the storage unit 12.

In a case where the frame rate f_(body) is equal to less than the framerate f_(acc) (step S3: NO), there is a possibility that sufficientperformance will not be acquired in the combination of the constantspeed control with the frame rate f_(body) from the fact that the framerate f_(body) is low even in a case where the priority specificationinformation Pmode specifies that the constant speed control ispreferentially performed.

Thus, the focusing speed and the focusing accuracy can be the best bycalculating the evaluation values in the combination of the accelerationand deceleration control with the frame rate f_(body).

In a case where the frame rate f_(body) is greater than the frame ratef_(acc) (step S3: YES), the process of step S6 or step S7 is performedaccording to the priority specification information Pmode. Thus, thefocusing speed and the focusing accuracy can be the best.

Since the lens device 40 is able to be attached to the digital camera,even in a case where the lens device 40 is replaced with another lensdevice, it is possible to set the combination of an optimum frame ratewith driving control based on the lens performance information and theframe rate f_(body).

Accordingly, it is possible to constantly realize the focusing controlat a high speed with high accuracy irrespective of the combination ofthe lens device with the digital camera.

It has been described in the digital camera of FIG. 1 that the lensperformance information stored in the lens device 40 includes the framerate face, the first movement speed V1, the second movement speed V2,and the deceleration a_(dec).

However, the information items of the first movement speed V1, thesecond movement speed V2, and the deceleration a_(dec) may be stored inthe storage unit 12 of the digital camera in advance.

For example, the information items of the first movement speed V1, thesecond movement speed V2, and the deceleration a_(dec) are stored in thestorage unit 12 for each device type ID of the lens device 40.

In a case where the search control unit 110 of the system control unit11 performs the acceleration and deceleration control, the accelerationand deceleration control may be performed based on the information itemscorresponding to the device type ID of the attached lens device 40.

Alternatively, only one set of the information items of the firstmovement speed V1, the second movement speed V2, and the decelerationa_(dec) may be stored in the storage unit 12 irrespective of the devicetype ID of the lens device 40, and the search control unit 110 mayperform the acceleration and deceleration control by using the set.

The information items of the first movement speed V1, the secondmovement speed V2, and the deceleration a_(dec) are stored in the lensdevice 40, and thus, it is possible to perform the acceleration anddeceleration control suitable for the lens device 40 even in a casewhere a new lens device 40 is released. It is not necessary to perform atask for storing the information items in the storage unit 12 of thedigital camera, and it is possible to reduce manufacturing cost of thedigital camera.

Hereinafter, modification examples of the digital camera shown in FIG. 1will be described.

First Modification Example

FIG. 5 is a diagram showing a modification example of a functional blockof the system control unit 11 shown in FIG. 2.

The system control unit 11 shown in FIG. 5 is realized by adding a framerate f_(acc) calculation unit 115 constituting a maximum imagingperformance information calculation unit to the system control unit 11shown in FIG. 2. The frame rate f_(acc) calculation unit 115 is formedby the focusing control program being executed by the processor.

Filter characteristic information of the filtering process performed ina case where the evaluation value calculation unit 111 calculates theevaluation values is further stored in the storage unit 12 of thedigital camera according to the first modification example.

The filter characteristic information corresponds to a movement distance(distance D_(peak) of FIG. 3) of the focus lens until the evaluationvalue reaches the peak after the change in evaluation value in the graphA2 shown in FIG. 3 which is equal to or greater than the threshold valueis started.

In the first modification example, the lens performance informationstored in the lens information storage unit 3 of the lens device 40 doesnot include the frame rate f_(acc). In addition to the priorityspecification information Pmode, the first movement speed V1, the secondmovement speed V2, and the deceleration a_(dec), the lens performanceinformation includes a movement amount f_(mh) of the focus lens allowedduring a one frame period in a case where the focus lens moves at thefirst movement speed V1, a movement amount f_(m) of the focus lensallowed during one frame period in a case where the focus lens moves atthe second movement speed V2, and a delay time t_(delay) until thedeceleration of the focus lens is actually started after an instructionto decelerate the movement speed of the focus lens is received from thesystem control unit 11 of the digital camera.

The movement amount f_(mh) of the focus lens, the movement amount f_(m)of the focus lens, the deceleration a_(dec), and the delay timet_(delay) constitute control information indicating driving ability ofthe focus lens in a case where the acceleration and deceleration controlis performed.

The frame rate f_(acc) calculation unit 115 calculates the maximum framerate f_(acc) at which the acceleration and deceleration control is ableto be performed in the lens device 40 based on the control informationacquired from the lens device 40 and the filter characteristicinformation stored in the storage unit 12.

Specifically, the frame rate f_(acc) calculation unit 115 calculates theframe rate f_(acc) by substituting the movement amount f_(mh) of thefocus lens acquired from the lens device 40, the movement amount f_(m)of the focus lens, the deceleration a_(dec), the delay time t_(delay),the filter characteristic information (distance D_(peak)) acquired fromthe storage unit 12 into Expression (2) obtained by solving Expression(1) for the frame rate f_(acc).

The units of the movement amount f_(mh) of the focus lens, the movementamount f_(m) of the focus lens, and the distance D_(peak) are “m”(meters). The unit of the delay time t_(delay) is “s” (seconds). Theunit of the deceleration a_(dec) is “m/s²”. The unit of the frame ratef_(acc) is “1/s”.

$\begin{matrix}{\left( \frac{f_{mh} - f_{m}}{1\text{/}f_{acc}} \right)^{2} = {2{a_{dec}\left( {D_{peak} - {\frac{f_{mh}}{1\text{/}f_{acc}}t_{delay}}} \right)}}} & {{Expression}\mspace{14mu} (1)} \\{f_{acc} = {{{- 2}a_{dec}f_{mh}t_{delay}} + \sqrt{\begin{matrix}{\left( {2a_{dec}f_{mh}t_{delay}} \right)^{2} +} \\{8\left( {f_{mh} - f_{m}} \right)^{2}a_{dec}D_{peak}}\end{matrix}}}} & {{Expression}\mspace{14mu} (2)}\end{matrix}$

As mentioned above, in the first modification example, it is assumedthat the maximum frame rate f_(acc) at which the acceleration anddeceleration control is able to be performed in the lens device 40 isacquired through the calculation.

In the first modification example, the priority specificationinformation Pmode included in the lens performance information isinformation indicating whether to preferentially perform the combinationof the frame rate f_(acc) acquired through the calculation with theacceleration and deceleration control or the combination of the imagingperformance information which is greater than the frame rate f_(acc)acquired through the calculation with the constant speed control.

FIG. 6 is a flowchart for describing an operation of the system controlunit 11 of the digital camera according to the first modificationexample. The flowchart shown in FIG. 6 is realized by adding step S2 bbetween step S2 and step S3 in the flowchart shown in FIG. 4.

After step S2, the frame rate f_(acc) calculation unit 115 calculatesthe frame rate f_(acc) based on the control information included in thelens performance information acquired in step S2 and the filtercharacteristic information stored in the storage unit 12 (step S2 b).Thereafter, step S3 and the subsequent processes are performed.

As stated above, in accordance with the digital camera according to thefirst modification example, it is possible to calculate the frame ratef_(acc) suitable for the combination of the lens device 40 with thedigital camera even in a case where the lens device 40 is replaced.

Thus, it is possible to accurately calculate the frame rate face, and itis possible to accurately determine whether to perform which process ofstep S4 to step S7. As a result, it is possible to perform the focusingcontrol at a high speed with high accuracy.

In the digital camera according to the first modification example, it isassumed that the lens performance information stored in the lens device40 includes the first movement speed V1, the second movement speed V2,the movement amount f_(mh) of the focus lens, the movement amount f_(m)of the focus lens, the deceleration a_(dec), and the delay timet_(delay).

However, the information items of the first movement speed V1, thesecond movement speed V2, the movement amount f_(mh) of the focus lens,the movement amount f_(m) of the focus lens, and the decelerationa_(dec) may be stored in the storage unit 12 of the digital camera inadvance.

For example, the information items of the first movement speed V1, thesecond movement speed V2, the movement amount f_(mh) of the focus lens,the movement amount f_(m) of the focus lens, and the decelerationa_(dec) are stored in the storage unit 12 for each device type ID of thelens device 40.

The frame rate f_(acc) calculation unit 115 of the system control unit11 may calculate the frame rate f_(acc) based on the informationcorresponding to the device type ID of the attached lens device 40, thefilter characteristic information stored in the storage unit 12, and thedelay time t_(delay) acquired from the lens device 40.

The search control unit 110 may perform the acceleration anddeceleration control based on the first movement speed V1, the secondmovement speed V2, and the deceleration a_(dec) included in theinformation corresponding to the device type ID of the attached lensdevice 40.

Second Modification Example

Although it has been described above that the priority specificationinformation Pmode is included in the lens performance information, thelens performance information may not include the priority specificationinformation Pmode. The operation of the system control unit 11 in thiscase will be described.

FIG. 7 is a flowchart for describing an operation of a system controlunit 11 of a digital camera according to the second modificationexample. The flowchart shown in FIG. 7 is realized by removing step S5and step S7 in the flowchart shown in FIG. 4 and performing step S6 in acase where the determination result of step S3 is YES.

For example, in a case where it is assumed that the lens device 40 is ashort-focus lens and the frame rate f_(body) is greater than the framerate f_(acc), it is possible to determine the target position at a highspeed with high accuracy in the combination of the frame rate f_(body)with the constant speed control compared to the combination of the framerate f_(acc) with the acceleration and deceleration control.

In a case where the frame rate f_(body) is sufficiently greater than theframe rate f_(acc) even though it is assumed that the lens device 40 isa long-focus lens, it is possible to determine the target position at ahigh speed with high accuracy in the combination of the frame ratef_(body) with the constant speed control compared to the combination ofthe frame rate f_(acc) with the acceleration and deceleration control.

As stated above, it is possible to achieve both the focusing speed andthe focusing accuracy even in the operation shown in FIG. 7.

Third Modification Example

A third modification example is realized by applying the secondmodification example to the first modification example.

FIG. 8 is a flowchart for describing an operation of a system controlunit 11 of a digital camera according to the third modification example.

The flowchart shown in FIG. 8 is realized by removing step S5 and stepS7 in the flowchart shown in FIG. 6 and performing step S6 in a casewhere the determination result of step S3 is YES.

For example, in a case where it is assumed that the lens device 40 is ashort-focus lens and the frame rate f_(body) is greater than the framerate f_(acc), it is possible to determine the target position at a highspeed with high accuracy in the combination of the frame rate f_(body)with the constant speed control compared to the combination of the framerate f_(acc) with the acceleration and deceleration control.

In a case where the frame rate f_(body) is sufficiently greater than theframe rate f_(acc) even though it is assumed that the lens device 40 isa long-focus lens, it is possible to determine the target position at ahigh speed with high accuracy in the combination of the frame ratef_(body) with the constant speed control compared to the combination ofthe frame rate f_(acc) with the acceleration and deceleration control.

As mentioned above, it is possible to achieve both the focusing speedand the focusing accuracy even in the operation shown in FIG. 8.

It has been described above that the frame rate is used as the imagingperformance information of the digital camera. However, the imagingperformance information may be a reciprocal of the frame rate, that is,a time (one frame period) required to acquire one captured image signal(one frame).

Hereinafter, a configuration of a smartphone as the imaging device willbe described.

FIG. 9 shows the appearance of a smartphone 200 which is an embodimentof an imaging device of the invention. The smartphone 200 shown in FIG.9 has a flat plate-shaped housing 201, and includes a display input unit204 in which a display panel 202 as a display unit on one surface of thehousing 201 and an operation panel 203 as an input unit are integrated.The housing 201 includes a speaker 205, a microphone 206, an operatingunit 207, and a camera unit 208. The configuration of the housing 201 isnot limited thereto, and for example, a configuration in which thedisplay unit and the input unit are independent from each other may beemployed, or a configuration having a folding structure or a slidemechanism may be employed.

FIG. 10 is a block diagram showing the configuration of the smartphone200 shown in FIG. 9. As shown in FIG. 10, principal components of thesmartphone include a wireless communication unit 210, a display inputunit 204, a call handling unit 211, an operating unit 207, a camera unit208, a storage unit 212, an external input/output unit 213, a globalpositioning system (GPS) receiving unit 214, a motion sensor unit 215, apower supply unit 216, and a main control unit 220. Principal functionsof the smartphone 200 include a wireless communication function ofperforming mobile wireless communication through a base station deviceBS (not shown) through a mobile communication network NW (not shown).

The wireless communication unit 210 performs wireless communication witha base station device BS in the mobile communication network NWaccording to an instruction of the main control unit 220. With the useof the wireless communication, transmission and reception of variouskinds of file data, such as voice data and image data, and electronicmail data, or reception of Web data, streaming data, or the like areperformed.

The display input unit 204 is a so-called touch panel which displaysimages (still images and moving images) or character information, or thelike to visually transfer information to the user and detects a user'soperation on the displayed information under the control of the maincontrol unit 220, and includes the display panel 202 and the operationpanel 203.

The display panel 202 uses a liquid crystal display (LCD), an organicelectro-luminescence display (OELD), or the like, as a display device.

The operation panel 203 is a device which is placed such that an imagedisplayed on a display surface of the display panel 202 is visible, anddetects one or a plurality of coordinates of an operation with a user'sfinger or a stylus. If the device is operated with the user's finger orthe stylus, a detection signal due to the operation is output to themain control unit 220. Next, the main control unit 220 detects anoperation position (coordinates) on the display panel 202 based on thereceived detection signal.

As shown in FIG. 10, although the display panel 202 and the operationpanel 203 of the smartphone 200 illustrated as an embodiment of animaging device of the invention are integrated to constitute the displayinput unit 204, the operation panel 203 is arranged to completely coverthe display panel 202.

In a case where this arrangement is employed, the operation panel 203may include a function of detecting a user's operation even in a regionoutside the display panel 202. In other words, the operation panel 203may include a detection region (hereinafter, referred to as a displayregion) for a superimposed portion overlapping the display panel 202 anda detection region (hereinafter, referred to as a non-display region)for an outer edge portion not overlapping the display panel 202 otherthan the display region.

Although the size of the display region may completely match the size ofthe display panel 202, it is not necessary to match both of the size ofthe display region and the size of the display panel. The operationpanel 203 may include two sensitive regions including an outer edgeportion and an inner portion other than the outer edge portion. Thewidth of the outer edge portion is appropriately designed according tothe size of the housing 201 or the like.

As a position detection system which is employed in the operation panel203, a matrix switching system, a resistive film system, a surfaceacoustic wave system, an infrared system, an electromagnetic inductionsystem, an electrostatic capacitance system, and the like areexemplified, and any system can be employed.

The call handling unit 211 includes the speaker 205 and the microphone206, converts voice of the user input through the microphone 206 tovoice data processable in the main control unit 220 and outputs voicedata to the main control unit 220, or decodes voice data received by thewireless communication unit 210 or the external input/output unit 213and outputs voice from the speaker 205.

As shown in FIG. 9, for example, the speaker 205 can be mounted on thesame surface as the surface on which the display input unit 204 isprovided, and the microphone 206 can be mounted on the side surface ofthe housing 201.

The operating unit 207 is a hardware key using a key switch or the like,and receives an instruction from the user. For example, as shown in FIG.9, the operating unit 207 is a push button-type switch which is mountedon the side surface of the housing 201 of the smartphone 200, and isturned on by being depressed with a finger or the like and is turned offby restoration force of the panel or the like in a case where the fingeris released.

The storage unit 212 stores a control program or control data of themain control unit 220, application software, address data in associationwith the name, telephone number, and the like of a communicationpartner, data of transmitted and received electronic mail, Web datadownloaded by Web browsing, and downloaded content data, and temporarilystores streaming data or the like. The storage unit 212 is constitutedof an internal storage unit 217 embedded in the smartphone and anexternal storage unit 218 having a slot for a detachable externalmemory.

The internal storage unit 217 and the external storage unit 218constituting the storage unit 212 are realized using a memory (forexample, a microSD (Registered Trademark) memory or the like), such as aflash memory type, a hard disk type, a multimedia card micro type, or acard type, or a storage medium, such as a random access memory (RAM) ora read only memory (ROM).

The external input/output unit 213 plays a role of an interface with allexternal devices connected to the smartphone 200, and is provided fordirect or indirect connection to other external devices throughcommunication or the like (for example, universal serial bus (USB), IEEE1394, or the like), or a network (for example, the Internet, wirelessLAN, Bluetooth (Registered trademark), radio frequency identification(RFID), infrared communication (Infrared Data Association: IrDA)(Registered Trademark), Ultra Wideband (UWB) (Registered Trademark),ZigBee (Registered Trademark), or the like).

The external devices connected to the smartphone 200 are, for example, awired or wireless headset, a wired or wireless external charger, a wiredor wireless data port, a memory card connected through a card socket, asubscriber identity module (SIM) card, a user identity module (UIM)card, an external audio-video device connected through an audio-videoinput/output (I/O) terminal, an external audio-video device connected ina wireless manner, a smartphone connected in a wired or wireless manner,a personal computer connected in a wired or wireless manner, an earphoneconnected in a wired or wireless manner, and the like. The externalinput/output unit 213 can transfer data transmitted from the externaldevices to the respective components in the smartphone 200 or cantransmit data in the smartphone 200 to the external devices.

The GPS receiving unit 214 receives GPS signals transmitted from GPSsatellites ST1 to STn according to an instruction of the main controlunit 220, executes positioning calculation processing based on aplurality of received GPS signals, and detects the position of thesmartphone 200 having latitude, longitude, and altitude. In a case wherepositional information can be acquired from the wireless communicationunit 210 or the external input/output unit 213 (for example, a wirelessLAN), the GPS receiving unit 214 can detect the position using thepositional information.

The motion sensor unit 215 includes, for example, a three-axisacceleration sensor or the like, and detects physical motion of thesmartphone 200 according to an instruction of the main control unit 220.The moving direction or acceleration of the smartphone 200 is detectedby detecting physical motion of the smartphone 200. The detection resultis output to the main control unit 220.

The power supply unit 216 supplies electric power stored in a battery(not shown) to the respective units of the smartphone 200 according toan instruction of the main control unit 220.

The main control unit 220 includes a microprocessor, operates accordingto the control program or control data stored in the storage unit 212,and integrally controls the respective units of the smartphone 200. Themain control unit 220 has a mobile communication control function ofcontrolling respective units of a communication system in order toperform voice communication or data communication through the wirelesscommunication unit 210, and an application processing function.

The application processing function is realized by the main control unit220 operating according to application software stored in the storageunit 212. The application processing function is, for example, aninfrared communication function of controlling the external input/outputunit 213 to perform data communication with a device facing thesmartphone 200, an electronic mail function of transmitting andreceiving electronic mail, a Web browsing function of browsing Webpages, or the like.

The main control unit 220 has an image processing function of displayingvideo on the display input unit 204, or the like based on image data(still image or moving image data), such as received data or downloadedstreaming data. The image processing function refers to a function ofthe main control unit 220 decoding image data, performing imageprocessing on the decoding result, and displaying an image on thedisplay input unit 204.

The main control unit 220 executes display control on the display panel202 and operation detection control for detecting a user's operationthrough the operating unit 207 and the operation panel 203. With theexecution of the display control, the main control unit 220 displays anicon for activating application software or a software key, such as ascroll bar, or displays a window for creating electronic mail.

The scroll bar refers to a software key for receiving an instruction tomove a display portion of an image which is too large to fit into thedisplay region of the display panel 202.

With the execution of the operation detection control, the main controlunit 220 detects a user's operation through the operating unit 207,receives an operation on the icon or an input of a character string inan entry column of the window through the operation panel 203, orreceives a scroll request of a display image through the scroll bar.

In addition, with the execution of the operation detection control, themain control unit 220 has a touch panel control function of determiningwhether an operation position on the operation panel 203 is thesuperimposed portion (display region) overlapping the display panel 202or the outer edge portion (non-display region) not overlapping thedisplay panel 202 other than the display region, and controlling thesensitive region of the operation panel 203 or the display position ofthe software key.

The main control unit 220 may detect a gesture operation on theoperation panel 203 and may execute a function set in advance accordingto the detected gesture operation. The gesture operation is not aconventional simple touch operation, but means an operation to render atrack with a finger or the like, an operation to simultaneouslydesignate a plurality of positions, or an operation to render a trackfor at least one of a plurality of positions by combining theabove-described operations.

The camera unit 208 includes the configuration other than the externalmemory control unit 20, the recording medium 21, the display controlunit 22, the display unit 23, and the operating unit 14 in the digitalcamera shown in FIG. 1.

Captured image data generated by the camera unit 208 can be recorded inthe storage unit 212 or can be output through the external input/outputunit 213 or the wireless communication unit 210.

In the smartphone 200 shown in FIG. 9, although the camera unit 208 ismounted on the same surface as the display input unit 204, the mountingposition of the camera unit 208 is not limited thereto, and the cameraunit 208 may be mounted on the rear surface of the display input unit204.

The camera unit 208 can be used for various functions of the smartphone200. For example, an image acquired by the camera unit 208 can bedisplayed on the display panel 202, or an image in the camera unit 208can be used as one operation input of the operation panel 203.

In a case where the GPS receiving unit 214 detects the position, theposition may be detected with reference to an image from the camera unit208. In addition, the optical axis direction of the camera unit 208 ofthe smartphone 200 can be determined or a current use environment may bedetermined with reference to an image from the camera unit 208 withoutusing the three-axis acceleration sensor or in combination with thethree-axis acceleration sensor. Of course, an image from the camera unit208 may be used in application software.

In addition, image data of a still image or a moving image may beattached with positional information acquired by the GPS receiving unit214, voice information (which may be converted to text informationthrough voice-text conversion by the main control unit or the like)acquired by the microphone 206, posture information acquired by themotion sensor unit 215, or the like and can be recorded in the storageunit 212, or may be output through the external input/output unit 213 orthe wireless communication unit 210.

In the smartphone 200 having the above-described configuration, it isalso possible to perform the subject tracking AF with high accuracy.

As described above, the following matters are disclosed in thisspecification.

Disclosed is an imaging device to which a lens device including a focuslens capable of moving in an optical axis direction is detachablyattached. The imaging device comprises an imaging element that images asubject through the focus lens, a search control unit that acquirescaptured image signals by causing the imaging element to image thesubject for each position of the focus lens while moving the focus lens,an evaluation value calculation unit that calculates evaluation valuesfor determining a target position of the focus lens based on thecaptured image signals, a target position determination unit thatdetermines the target position of the focus lens based on the evaluationvalues, a focusing control unit that moves the focus lens to the targetposition, a storage unit that stores first imaging performanceinformation indicating the number of captured image signals read out perunit time in a case where the captured image signals are continuouslyread out from the imaging element or a reading interval in a case wherethe captured image signals are read out, and a lens informationacquisition unit that acquires lens performance information indicatingfocusing performance of the focus lens from the lens device. The searchcontrol unit selectively performs any one of acceleration anddeceleration control such that a movement speed of the focus lens isdecelerated after the movement speed is accelerated and constant speedcontrol such that the movement speed of the focus lens is constant bycontrolling the movement speed based on the evaluation values, based onthe lens performance information and the first imaging performanceinformation.

In the disclosed imaging device, the lens performance informationincludes maximum second imaging performance information capable of beingcombined with the acceleration and deceleration control.

In the disclosed imaging device, the lens performance informationfurther includes priority specification information indicating whetherto preferentially perform a combination of the second imagingperformance information with the acceleration and deceleration controlor a combination of imaging performance information greater than thesecond imaging performance information with the constant speed control.

In the disclosed imaging device, the lens performance informationincludes control information indicating driving ability of the focuslens in a case where the acceleration and deceleration control isperformed, the evaluation value calculation unit performs a filteringprocess on the captured image signals, and calculates the evaluationvalues based on signals acquired through the filtering process, and theimaging device further includes a maximum imaging performanceinformation calculation unit that calculates maximum second imagingperformance information with which the acceleration and decelerationcontrol is able to be performed based on the control informationacquired from the lens device and filter characteristic information ofthe filtering process.

In the disclosed imaging device, the lens performance informationfurther includes priority specification information indicating whetherto preferentially perform a combination of the maximum second imagingperformance information with which the acceleration and decelerationcontrol is able to be performed with the acceleration and decelerationcontrol or a combination of imaging performance information greater thanthe maximum second imaging performance information with the constantspeed control.

In the disclosed imaging device, the control information includes amovement amount of the focus lens allowed during one frame period of thefocus lens at the time of the acceleration and deceleration control, adeceleration at which the focus lens is decelerated, and a delay time towhen the deceleration of the focus lens is started from when aninstruction to start the deceleration of the focus lens is received fromthe imaging device.

In the disclosed imaging device, the search control unit drives theimaging element and performs the acceleration and deceleration controlaccording to the first imaging performance information in a case wherethe first imaging performance information is equal to or less than thesecond imaging performance information, and determines whether to drivethe imaging element and perform the acceleration and decelerationcontrol according to the second imaging performance information or todrive the imaging element and perform the constant speed controlaccording to the first imaging performance information based on thepriority specification information in a case where the first imagingperformance information exceeds the second imaging performanceinformation.

Disclosed is a focusing control method using an imaging device to whicha lens device including a focus lens capable of moving in an opticalaxis direction is detachably attached and which has an imaging elementwhich images a subject through the focus lens. The method comprises asearch control step of acquiring captured image signals by causing theimaging element to image the subject for each position of the focus lenswhile moving the focus lens, an evaluation value calculation step ofcalculating evaluation values for determining a target position of thefocus lens based on the captured image signals, a target positiondetermination step of determining the target position of the focus lensbased on the evaluation values, a focusing control step of moving thefocus lens to the target position, and a lens information acquisitionstep of acquiring lens performance information indicating focusingperformance of the focus lens from the lens device. In the searchcontrol step, any one of acceleration and deceleration control such thata movement speed of the focus lens is decelerated after the movementspeed is accelerated and constant speed control such that the movementspeed of the focus lens is constant is selectively performed bycontrolling the movement speed based on the evaluation values, based onthe lens performance information and first imaging performanceinformation stored in a storage unit within the imaging device whichstores imaging performance information indicating the number of capturedimage signals read out per unit time in a case where the captured imagesignals are continuously read out from the imaging element or a readinginterval of the captured image signals.

In the disclosed focusing control method, the lens performanceinformation includes maximum second imaging performance informationcapable of being combined with the acceleration and decelerationcontrol.

In the disclosed focusing control method, the lens performanceinformation further includes priority specification informationindicating whether to preferentially perform a combination of the secondimaging performance information with the acceleration and decelerationcontrol or a combination of imaging performance information greater thanthe second imaging performance information with the constant speedcontrol.

In the disclosed focusing control method, the lens performanceinformation includes control information indicating driving ability ofthe focus lens in a case where the acceleration and deceleration controlis performed, in the evaluation value calculation step, a filteringprocess is performed on the captured image signals, and the evaluationvalues are calculated based on signals acquired through the filteringprocess, and the focusing control method further includes a maximumimaging performance information calculation step of calculating maximumsecond imaging performance information with which the acceleration anddeceleration control is able to be performed based on the controlinformation acquired from the lens device and filter characteristicinformation of the filtering process.

In the disclosed focusing control method, the lens performanceinformation further includes priority specification informationindicating whether to preferentially perform a combination of themaximum second imaging performance information with which theacceleration and deceleration control is able to be performed with theacceleration and deceleration control or a combination of imagingperformance information greater than the maximum second imagingperformance information with the constant speed control.

In the disclosed focusing control method, the control informationincludes a movement amount of the focus lens allowed during one frameperiod of the focus lens at the time of the acceleration anddeceleration control, a deceleration at which the focus lens isdecelerated, and a delay time to when the deceleration of the focus lensis started from when an instruction to start the deceleration of thefocus lens is received from the imaging device.

In the disclosed focusing control method, in the search control step,the imaging element is driven and the acceleration and decelerationcontrol is performed according to the first imaging performanceinformation in a case where the first imaging performance information isequal to or less than the second imaging performance information, and itis determined whether to drive the imaging element and perform theacceleration and deceleration control according to the second imagingperformance information or to drive the imaging element and perform theconstant speed control according to the first imaging performanceinformation based on the priority specification information in a casewhere the first imaging performance information exceeds the secondimaging performance information.

Disclosed is a focusing control program causing a computer included inan imaging device to which a lens device including a focus lens capableof moving in an optical axis direction is detachably attached and whichhas an imaging element which images a subject through the focus lens tofunction as a search control unit that acquires captured image signalsby causing the imaging element to image the subject for each position ofthe focus lens while moving the focus lens, an evaluation valuecalculation unit that calculates evaluation values for determining atarget position of the focus lens based on the captured image signals, atarget position determination unit that determines the target positionof the focus lens based on the evaluation values, a focusing controlunit that moves the focus lens to the target position, and a lensinformation acquisition unit that acquires lens performance informationindicating focusing performance of the focus lens from the lens device.The search control unit selectively performs any one of acceleration anddeceleration control such that a movement speed of the focus lens isdecelerated after the movement speed is accelerated and constant speedcontrol such that the movement speed of the focus lens is constant bycontrolling the movement speed based on the evaluation values, based onthe lens performance information and imaging performance informationstored in a storage unit within the imaging device which stores imagingperformance information indicating the number of captured image signalsread out per unit time in a case where the captured image signals arecontinuously read out from the imaging element or a reading interval ofthe captured image signals.

The invention is applied to, in particular, a digital camera or thelike, thereby achieving high convenience and effectiveness.

Although the invention has been described above by a specificembodiment, the invention is not limited to the embodiment, and variousmodifications may be made without departing from the technical spirit ofthe invention disclosed herein. This application is based on JapanesePatent Application (JP2015-249618), filed Dec. 22, 2015, the content ofwhich is incorporated herein.

EXPLANATION OF REFERENCES

-   -   1: imaging lens    -   2: stop    -   3: lens information storage unit    -   4: lens control unit    -   5: imaging element    -   6: analog signal processing unit    -   7: analog-to-digital conversion circuit    -   8: lens drive unit    -   9: stop drive unit    -   10: imaging element drive unit    -   11: system control unit    -   12: storage unit    -   14: operating unit    -   15: memory control unit    -   16: main memory    -   17: digital signal processing unit    -   18: compression/expansion processing unit    -   20: external memory control unit    -   21: recording medium    -   22: display control unit    -   23: display unit    -   24: control bus    -   25: data bus    -   110: search control unit    -   111: evaluation value calculation unit    -   112: target position determination unit    -   113: focusing control unit    -   114: lens information acquisition unit    -   115: frame rate face calculation unit    -   200: smartphone    -   201: housing    -   202: display panel    -   203: operation panel    -   204: display input unit    -   205: speaker    -   206: microphone    -   207: operating unit    -   208: camera unit    -   210: wireless communication unit    -   211: call handling unit    -   212: storage unit    -   213: external input/output unit    -   214: GPS receiving unit    -   215: motion sensor unit    -   216: power supply unit    -   217: internal storage unit    -   218: external storage unit    -   220: main control unit    -   ST1 to STn: GPS satellite

What is claimed is:
 1. An imaging device comprising: a lens comprising afocus lens capable of moving in an optical axis direction; an imagingelement imaging a subject through the focus lens; a processor,configured to: control the focus lens and the imaging element to acquirecaptured image signals by causing the imaging element to image thesubject for each position of the focus lens while moving the focus lens;calculate evaluation values for determining a target position of thefocus lens based on the captured image signals; determine the targetposition of the focus lens based on the evaluation values; acquire lensperformance information indicating focusing performance of the focuslens from the lens, wherein one of acceleration and deceleration controlare selectively performed such that a movement speed of the focus lensis decelerated after the movement speed is accelerated and constantspeed control such that the movement speed of the focus lens is constantby controlling the movement speed based on the evaluation values, thelens performance information, and imaging performance informationindicating a number of captured image signals read out per unit time ina case where the captured image signals are continuously read out fromthe imaging element or a reading interval of the captured image signalsso as to move the focus lens to the target position.
 2. The imagingdevice according to claim 1, wherein the lens performance informationcomprises maximum second imaging performance information capable ofbeing combined with the acceleration and deceleration control.
 3. Theimaging device according to claim 2, wherein the lens performanceinformation further comprises priority specification informationindicating whether to preferentially perform a combination of the secondimaging performance information with the acceleration and decelerationcontrol or a combination of imaging performance information beinggreater than the second imaging performance information with theconstant speed control.
 4. The imaging device according to claim 1,wherein the lens performance information comprises control informationindicating driving ability of the focus lens in a case where theacceleration and deceleration control is performed, the processorperforms a filtering process on the captured image signals, andcalculates the evaluation values based on signals acquired through thefiltering process, and the processor further calculates maximum secondimaging performance information with which the acceleration anddeceleration control is able to be performed based on the controlinformation acquired from the lens and filter characteristic informationof the filtering process.
 5. The imaging device according to claim 4,wherein the lens performance information further comprises priorityspecification information indicating whether to preferentially perform acombination of the maximum second imaging performance information withwhich the acceleration and deceleration control is able to be performedwith the acceleration and deceleration control or a combination ofimaging performance information being greater than the maximum secondimaging performance information with the constant speed control.
 6. Theimaging device according to claim 4, wherein the control informationcomprises a movement amount of the focus lens allowed during one frameperiod of the focus lens at a time of the acceleration and decelerationcontrol, a deceleration at which the focus lens is decelerated, and adelay time to when the deceleration of the focus lens is started fromwhen an instruction to start the deceleration of the focus lens isreceived from the imaging device.
 7. The imaging device according toclaim 5, wherein the control information comprises a movement amount ofthe focus lens allowed during one frame period of the focus lens at atime of the acceleration and deceleration control, a deceleration atwhich the focus lens is decelerated, and a delay time to when thedeceleration of the focus lens is started from when an instruction tostart the deceleration of the focus lens is received from the imagingdevice.
 8. The imaging device according to claim 3, wherein theprocessor drives the imaging element and performs the acceleration anddeceleration control according to the first imaging performanceinformation in a case where the first imaging performance information isequal to or less than the second imaging performance information, anddetermines whether to drive the imaging element and perform theacceleration and deceleration control according to the second imagingperformance information or to drive the imaging element and perform theconstant speed control according to the first imaging performanceinformation based on the priority specification information in a casewhere the first imaging performance information exceeds the secondimaging performance information.
 9. The imaging device according toclaim 5, wherein the processor drives the imaging element and performsthe acceleration and deceleration control according to the first imagingperformance information in a case where the first imaging performanceinformation is equal to or less than the second imaging performanceinformation, and determines whether to drive the imaging element andperform the acceleration and deceleration control according to thesecond imaging performance information or to drive the imaging elementand perform the constant speed control according to the first imagingperformance information based on the priority specification informationin a case where the first imaging performance information exceeds thesecond imaging performance information.
 10. A focusing control methodusing an imaging device having a lens comprising a focus lens capable ofmoving in an optical axis direction and having an imaging element whichimages a subject through the focus lens, the method comprising: a searchcontrol step of controlling the focus lens and the imaging element toacquire captured image signals by causing the imaging element to imagethe subject for each position of the focus lens while moving the focuslens; an evaluation value calculation step of calculating evaluationvalues for determining a target position of the focus lens based on thecaptured image signals; a target position determination step ofdetermining the target position of the focus lens based on theevaluation values; and a lens information acquisition step of acquiringlens performance information indicating focusing performance of thefocus lens from the lens, wherein, in the search control step, one ofacceleration and deceleration control such that a movement speed of thefocus lens is decelerated after the movement speed is accelerated andconstant speed control such that the movement speed of the focus lens isconstant is selectively performed by controlling the movement speedbased on the evaluation values, the lens performance information, andfirst imaging performance information indicating a number of capturedimage signals read out per unit time in a case where the captured imagesignals are continuously read out from the imaging element or a readinginterval of the captured image signals so as to move the focus lens tothe target position.
 11. The focusing control method according to claim10, wherein the lens performance information comprises maximum secondimaging performance information capable of being combined with theacceleration and deceleration control.
 12. The focusing control methodaccording to claim 11, wherein the lens performance information furthercomprises priority specification information indicating whether topreferentially perform a combination of the second imaging performanceinformation with the acceleration and deceleration control or acombination of imaging performance information being greater than thesecond imaging performance information with the constant speed control.13. The focusing control method according to claim 10, wherein the lensperformance information comprises control information indicating drivingability of the focus lens in a case where the acceleration anddeceleration control is performed, in the evaluation value calculationstep, a filtering process is performed on the captured image signals,and the evaluation values are calculated based on signals acquiredthrough the filtering process, and the focusing control method furthercomprises a maximum imaging performance information calculation step ofcalculating maximum second imaging performance information with whichthe acceleration and deceleration control is able to be performed basedon the control information acquired from the lens and filtercharacteristic information of the filtering process.
 14. The focusingcontrol method according to claim 13, wherein the lens performanceinformation further comprises priority specification informationindicating whether to preferentially perform a combination of themaximum second imaging performance information with which theacceleration and deceleration control is able to be performed with theacceleration and deceleration control or a combination of imagingperformance information being greater than the maximum second imagingperformance information with the constant speed control.
 15. Thefocusing control method according to claim 13, wherein the controlinformation comprises a movement amount of the focus lens allowed duringone frame period of the focus lens at a time of the acceleration anddeceleration control, a deceleration at which the focus lens isdecelerated, and a delay time to when the deceleration of the focus lensis started from when an instruction to start the deceleration of thefocus lens is received from the imaging device.
 16. The focusing controlmethod according to claim 14, wherein the control information comprisesa movement amount of the focus lens allowed during one frame period ofthe focus lens at a time of the acceleration and deceleration control, adeceleration at which the focus lens is decelerated, and a delay time towhen the deceleration of the focus lens is started from when aninstruction to start the deceleration of the focus lens is received fromthe imaging device.
 17. The focusing control method according to claim12, wherein, in the search control step, the imaging element is drivenand the acceleration and deceleration control is performed according tothe first imaging performance information in a case where the firstimaging performance information is equal to or less than the secondimaging performance information, and whether to drive the imagingelement and perform the acceleration and deceleration control accordingto the second imaging performance information or to drive the imagingelement and perform the constant speed control according to the firstimaging performance information is determined based on the priorityspecification information in a case where the first imaging performanceinformation exceeds the second imaging performance information.
 18. Thefocusing control method according to claim 14, wherein, in the searchcontrol step, the imaging element is driven and the acceleration anddeceleration control is performed according to the first imagingperformance information in a case where the first imaging performanceinformation is equal to or less than the second imaging performanceinformation, and whether to drive the imaging element and perform theacceleration and deceleration control according to the second imagingperformance information or to drive the imaging element and perform theconstant speed control according to the first imaging performanceinformation is determined based on the priority specificationinformation in a case where the first imaging performance informationexceeds the second imaging performance information.
 19. A non-transitorycomputer readable medium storing a focusing control program causing acomputer included in an imaging device having a lens comprising a focuslens capable of moving in an optical axis direction and having animaging element which images a subject through the focus lens to:control the focus lens and the imaging element to acquire captured imagesignals by causing the imaging element to image the subject for eachposition of the focus lens while moving the focus lens; calculateevaluation values for determining a target position of the focus lensbased on the captured image signals; determine the target position ofthe focus lens based on the evaluation values; acquire lens performanceinformation indicating focusing performance of the focus lens from thelens, wherein one of acceleration and deceleration control areselectively performed such that a movement speed of the focus lens isdecelerated after the movement speed is accelerated and constant speedcontrol such that the movement speed of the focus lens is constant bycontrolling the movement speed based on the evaluation values, the lensperformance information, and imaging performance information indicatinga number of captured image signals read out per unit time in a casewhere the captured image signals are continuously read out from theimaging element or a reading interval of the captured image signals soas to move the focus lens to the target position.